1. Field of the Invention
The present invention relates to a solar battery, and more particularly to a solar battery cooling structure.
2. Description of the Related Art
Generally, a solar cell tends to have decreased power generation capability as its temperature rises. For example, when the temperature of a solar cell rises up to 100.degree. C., its power generation capability decreases by about 60% compared to that at 25.degree. C. Hence, various solar cell cooling techniques have been conventionally proposed to suppress a fall in power generation and to improve the durability. Such a solar cell cooling technique is disclosed in Japanese patent laid-open publication Hei 5-83881. This publication teaches the technique of immersing a solar cell element into water according to a cooling jacket system. In this example, a solar module is formed by arranging solar cells and then covering the intermediate product with a waterproof resin. Hence, it is considered that the solar cells are indirectly cooled via the resin.
However, in order to reduce energy recovering years or energy payback term (years in which the energy used for production of a solar module can be recovered as generated power) and to reduce the cost of building a solar-cell built-in power generating system, much attention has recently been focused on the light-gathering-type solar module that gathers the sunlight using a condenser, thus increasing the incident light amount on a solar cell and reducing the use area for expensive solar cells. In such a light-gathering solar module unit, since the temperature of the solar cell rises significantly with an increase of the light condensing degree, it is difficult to obtain a sufficient cooling effect in the conventional cooling method. In order to cool the solar cell effectively and efficiently, the solar cell may be directly cooled with a coolant. A technique of directly cooling a solar cell is shown in FIG. 5. Referring to FIG. 5, the solar cell 10 is formed on the substrate 100. The generated power is taken out of the electrodes 12 formed on the rear surface of the solar cell 10 via the bus lines 102. Bank-like reinforced portions 14 are formed around the fringe of the light receiving surface of the solar cell 10. The sealing agent 104 such as an epoxy resin seals surfaces ranging from the reinforced portion 14 to the substrate 100 and is filled in the gap between the solar cell 10 and the substrate 100. Even when the solar cell 10 is directly cooled with a coolant such as water, this sealing agent prevents the coolant from flowing onto the electrode 12. As a result, the electrode can be prevented from being corroded. However, when the solar cell is used for a long period of time, the solar cell 10 experiences repetitive changes in temperature. The difference in thermal expansion coefficient between silicon, or a material forming the solar cell 10, and the sealing agent 104 causes the sealing agent 104 to come away from the solar cell 10. It is considered that this coming away occurs when the solar cell is used for 2 to 6 years. For that reason, there is the problem in that the coolant is leaked from the interface between the solar cell 10 and the sealing agent 104 to the electrode 12, thus corroding the electrode 12.